1. Field of the Invention
This invention relates to a self-holding switch for use in a sound reproducing device. More particularly, the present invention relates to a self-holding switch in which a movable contact is fabricated of a spring wire, a medical or halfway portion of which is wound around a pin and its one free end is rested on the casing of a sound reproducing device, while the other free end is rested on the medial or halfway portion of a lever which is received by the pin and, also, is coaxial with the movable contact.
2. Prior Art
Sound reproducing devices, particularly, the most simplified of sound reproducing devices, are constructed to have a pickup normally urged toward the starting point of sound reproduction by a return spring. The pickup is held in position by the resilient force of the return spring. When the pickup has returned to the starting point of sound reproduction for the next playing, the movable contact of a self-holding switch, which had previously been positioned at the starting point of sound reproduction, is detached from engagement with the fixed contact and cuts off the power to a motor driving the record disc. In this kind of sound reproducing device, the motor, which rotates the record disc, is started by a starting switch connected in parallel to the self-holding switch. Then, the movable contact of the self-holding switch held in place by the pickup is released by the movement of the pickup from the starting point toward the end point of sound reproduction, subsequent to the starting of the record disc. This results in contact between the movable contact and the fixed contact which, in turn, completes an electrical circuit for driving the motor, even when the starting switch is placed in the "off" position when the operator takes his or her hand off the device.
However, in such a self-holding switch, the movable contact has ordinarily been fabricated from a flat strip, defining a leaf spring, which makes contact with a mating fixed contact by virtue of its resilient property. Accordingly, this requires using material with strong spring properties in order to ensure sufficient contact pressure between the movable contact and the fixed contact.
However, on the other hand, it has been a common practice in designing a return spring, for urging the pickup, to have a comparatively weak spring property which is sufficient, only, to return the light weight pickup, but not so strong as to take the stylus of the pickup out of engagement with the recorded groove. Consequently, it is impossible, with prior art devices, to use a movable contact made of a material having a high spring property. This use of material with weak spring property material has caused insufficient contact pressure, which results in various kinds of malfunctions.
In addition, if such a leaf spring is directly applied, as the movable contact of a self-holding switch, locational adjustment of the contact, with respect both to the mating fixed contact and to the location of the returning point of the pickup, becomes very difficult. This is due to the relation between the spring property of the relating parts, thereby rendering the setting thereof very difficult.
Furthermore, use of such leaf spring is liable to cause, in mass production, lack of uniformity in the spring length necessary for positioning it to the specific returning point of the pickup. This results in variations in the moment of force given by the movable contact to the pickup, which holds the movable contact in position. This invention aims to obviate such drawbacks as mentioned above.